1. Field of the Invention
The present invention relates to a roll threading apparatus for threading a tubular flange around an aperture defined in an end blank for use on a metal drum container.
2. Description of the Prior Art
Heretofore, it has been customary in the metal drum container industries to thread a tubular flange, which is separate from an end blank for use on a metal drum container, to form internal threads for engaging a plug, and then attaching the threaded flange to the end blank. Roll threading has been used to thread such tubular flanges.
Recently, it has been proposed to produce end blank with integral tubular flanges. However, threading tubular flanges that are integral with end blanks by way of roll threading cannot be performed by conventional roll threading apparatus because the end blank, which is relatively heavy, has to be rotated together with the tubular flange. Accordingly, it is necessary to thread tubular flanges integral with end blanks by way of tapping. When a tubular flange is tapped, however, the mechanical strength of the flange is lowered, and chips need to be removed.